This invention relates to a field emission electron gun including a plurality of sharp-pointed emitters.
A field emission electron gun includes an emitter for emitting electrons and an anode electrode. The emitter is of a sharp pointed shape for concentrating an electric field. In general, a plurality of emitters are integrated in order to increase a total current of the field emission electron gun. The field emission electron gun further includes a first gate electrode surrounding the emitter with a space left therebetween and having an outer peripheral surface defining an emission region. A second gate electrode surrounds the outer peripheral surface of the first gate electrode with a distance left therebetween.
The field emission electron gun is employed for a wide range of applications. If the field emission electron gun is used in a planar display device, a fluorescent member is located at a distance on the order of 1 mm from the electron gun. Electrons are emitted from the emitters of the emission region as an electron beam towards the fluorescent member.
Naturally, the electron beam is emitted with a particular diverging angle. If the diverging angle is large, the electron beam can not form a sufficiently small diameter or cross-sectional area on the fluorescent member. This decreases the luminance of the fluorescent member.
Empirically, it has been confirmed that the diverging angle ranges between 20 and 30 degrees. In order to assure a sufficient luminance, various proposals have been made to suppress the diverging angle. For example, Japanese Unexamined Patent Publications (JP-A) Nos. 343000/1993, 242794/1993, 266806/1993, and 29484/1995 disclose the use of a deflection electrode or a focusing electrode to cause repulsion of electrons so as to suppress the divergence of the electron beam.
As will later be described, a conventional field emission electron gun is incapable of minimizing nonuniform influence of a surrounding electric potential condition on electrons emitted from emitters of the emission region.